Chamaecrista tenuicaulis A. O. Souza & M. J. Silva, 2015

Souza, Alessandro Oliveira De & Silva, Marcos José Da, 2015, A new species of Chamaecrista (Leguminosae) from the Brazilian Central Plateau, Phytotaxa 204 (2), pp. 165-171 : 166-167

Chamaecrista tenuicaulis A. O. Souza & M. J. Silva , sp. nov. ( Figure 1 )

Species more morphologically similar to C. decumbens (Benth.) H.S. Irwin & Barneby and C. benthamiana (Harms) H.S. Irwin & Barneby but differing from them by a set of characteristics such as growth habit, size of leaflets and its relation with the size of rachis, presence of indumentum on leaves and stems, inflorescence aspect, including number of flowers, and pedicel length.

Type: — BRAZIL. Goiás: Alto Paraíso de Goiás, Chapada dos Veadeiros, Parque Nacional da Chapada dos Veadeiros, estrada de terra para a Fazenda Bona Espero, em campo, 14º05’12.3” S, 47º38’12.4” W, 1175 m elev., 13 Jul 2013, (fl.), A. O. Souza, M. J. Silva, P. H. B. Santos & R. B. Araújo 554 (holotype: UFG!; isotypes: UB!, CEN!, NY!) .

Subshrub 15–35 cm tall, subdecumbent, cespitose, arising from a xylopodium. Branches 18–60 cm long, cylindrical, slender, greenish to brownish, inconspicuously villous and setulose, including petiole and rachis. Stipules 1.8–4.7 × 0.1–0.2 mm, linear, pubescent and setulose to glabrous, persistent. Leaves 3.5–7(–9) cm long, alternate, spiral, petiolate; extrafloral nectary absent; petiole 0.5–1.5(–2) cm long, yellow-greenish; rachis 2–5.5 cm long, sulcated above, yellow-greenish; interfoliolar segments 0.5–1.2(–1.5) cm long; leaflets (3–)4–7(–11) pairs, divaricate along the rachis, blade 0.9–1.4(–2) × 0.6–1.2(–1.5) cm, elliptic to obovate, base slightly oblique, margin plane, entire, glabrous on both surfaces, obtuse to acute, rarely emarginate and shortly mucronulate, concolorous, greenish to olivaceous, carthaceous; venation brochidodromous, midrib and secondary veins prominent only on the abaxial surface. Racemes 5.5–16 cm long, 6–15(–20) flowers, terminal, lax, erect, straight to slightly curved, slender, continuous with the leafy stem, axis viscose-setulose and villous, including pedicel, and external surface of the bracts, bracteoles, and sepals. Bracts 1.5–2 × 0.4–0.5 mm, lanceolate, persistent. Buds 0.5–1 × 0.4–0.6 cm, ovoid to ellipsoid, obtuse or abruptly apiculate at apex. Flowers 1.3–2 × 1–2 cm; pedicel 1.5–3 cm long, fruiting pedicel 1.7–3 cm long, cylindrical, slender, greenish to brownish; bracteoles 1.5–2 × 0.4–0.5 mm, lanceolate, alternate, situated between the middle and upper third of the pedicel, yellowish, persistent; sepal 0.8–1.2 × 0.3–0.4 cm, oblong to elliptic, acute or obtuse at apex, greenish to reddish on external surface; petals 1.2–2.2 × 0.9–1.7 cm, obovate to widely obovate, the inner petals falcate-asymmetric, golden yellow; stamens fertile 10, 4–6 mm long; anthers pubescent on lateral sutures, emarginate and shortly mucronulate at apex; ovary 4–5 × 1.5 mm, oblong, densely villous-setose, yellowish; styles 0.9–1.2 cm long, glabrous, slightly curved at apex, stigma punctiform. Pod 2–3.5 × 0.5–0.7 cm, oblong, villous-setulose, with thickened margin, light brown to dark brown when mature. Seeds 5–5.5 × 2.5–3.5 mm, oblong to obovoid, ochraceous to black, glossy.

Additional specimens examined (paratypes): — BRAZIL. Goiás: Alto Paraíso de Goiás, Parque Nacional da Chapada dos Veadeiros ( PNCV), proximidades da entrada para o alojamento dos brigadistas do PNCV em direção à vila São Jorge , 14º09’37.3” S, 47º46’29.7” W, 810 m elev., 21 Jun 2013, (fl., fr.), A. O. Souza et al. 413, 415 ( UFG) ; ib., subida em direção aos alojamentos do PNCV, em campo úmido, 14º09’37.3” S, 47º46’29.7” W, 810 m elev., 11 July 2013, (fl.), M. J. Silva et al. 5102 ( UFG) ; ib., PNCV, trilha em direção ao rio Preto, atrás do Morro da Baleia , em cerrado sensu stricto, 14º05’12.3” S, 47º38’12.4” W, 1175 m elev., 13 July 2013, (fl., fr.), A. O. Souza et al. 577, 578, 579, 580, 581 ( UFG) ; ib., PNCV, após o rio Preto em direção ao morro ao norte da fazenda Bona Espero , 14º02’57.3” S, 47º39’34.7” W, 1175 m elev., 13 July 2013, (fl., fr.), A. O. Souza et al. 586, 587, 600, 602 ( UFG) ; ib., 7 km a partir do Morro da Baleia em direção ao rio Preto , em cerrado sensu stricto, entre as gramíneas, 14º05’12.3” S, 47º38’12.4” W, 1175 m elev., 13 July 2013, (fl., fr.), M. J. Silva et al. 5144, 5146, 5147, 5148 ( UFG) ; ib., Cavalcante, 500 m após o rio Preto em direção ao Morro Peito de Moça , em campo úmido, entre as gramíneas, 14º05’12.3” S, 47º38’12.4” W, 1175 m elev., 13 July 2013, (fl., fr.), M. J. Silva et al. 5155, 5157 ( UFG) ; ib., a cerca de 1 km do Morro Peito de Moça , em campo úmido, 14º02’57.3” S, 47º39’34.7” W, 1175 m elev., 3 August 2013, (fl., fr.), M. J. Silva, L. L. C. Antunes & R. C. Sodré 5255, 5256 ( UFG) ; ib., PNCV, nas proximidades do topo do Morro da Baleia , 14º07’11.2” S, 47º38’50.5” W, 1385 m elev., 7 September 2013, (fl.), A. O. Souza, M. J. Silva, P. H. B. Santos, R. B. Araújo & R. C. Sodré 679 ( UFG) ; ib., PNCV, nas proximidades do topo do Morro da Baleia , 14º07’11.2” S, 47º38’50.5” W, 1385 m elev., 7 September 2013, (fl., fr.), M. J. Silva, A. O. Souza, P. H. B. Santos, R. B. Araújo & R. C. Sodré 5385, 5386, 5387, 5395, 5402, 5403, 5409 ( UFG) ; ib., em direção ao rio Preto , em borda de cerrado entre as gramíneas, 14º03’56.2” S, 47º38’18” W, 1198 m elev., 5 September 2014, (fl., fr.), A. O. Souza, C. C. Oliveira, L. S. Inocencio, M. J. Silva, N. C. Carvalho & R. C. Sodré 1261, 1262, 1263, 1264, 1265, 1266, 1267, 1268, 1269, 1270, 1271 ( UFG) ; ib., após o rio Preto, a 5 km do Morro Peito de Moça , em campo limpo, 14º02’57.2” S, 47º38’59.2” W, 1180 m elev., 5 September 2014, (fl., fr.), A. O. Souza et al.1273 ( UFG) .

Distribution and ecology: —Species so far restricted to the Chapada dos Veadeiros region, where it was collected in the municipalities of Alto Paraíso de Goiás and Cavalcante. It grows mainly in grassland vegetation (clean or rocky fields), but also on the edges of cerrado sensu stricto and cerrado rupestre, among grasses on clayey and gravelly soils, from 810 m to 1385 m elev.

Phenology: —Flowering and fruiting from June to September, but with more intense flowering between July and August.

Etymology: —The specific epithet tenuicaulis is a combination of the Latin words “ tenue ” (slender) and “ caulis ” (trunk or stem), and was chosen due to the slender and delicate branches of the new species.

Conservation status: — The new species has restricted distribution and populations of less than 1000 individuals. Additionally, the region surrounding the area of its occurrence is subject to intense tourist visitation and agricultural activities. Therefore, C. tenuicaulis is herein classified in category VU D 1.2 [VU: vulnerable; D: criteria for very small (1) or restricted (2) populations] of IUCN (2014).

Relationships and systematic position: —Based on the absence of extrafloral nectaries, presence of glandular trichomes at least on the axis of the inflorescence and pedicel, flowers with a distinct inner petal, divaricate and carthaceous leaflets, and racemose inflorescence, the new species was allocated in Chamaecrista sect. Absus subsect. Absus ( Colladon 1816: 116) H.S Irwin & Barneby (1982: 644) series Rigidulae (Benth.) H.S Irwin & Barneby , which encompasses 25 species, all endemic to Brazil, mainly distributed in the state of Goiás, where 20 of them are registered, eight of which are endemic ( Irwin & Barneby 1982).

Among the species of Rigidulae series, C. tenuicaulis resembles C. benthamiana ( Harms 1924: 128) Irwin & Barneby (1982: 654) and C. decumbens ( Bentham 1840: 79) Irwin & Barneby (1982: 654) because of its subshrubby habit. However, it differs from C. benthamiana for having subdecumbent (vs. creeping) habit, petiolate leaves (vs. sessile or subsessile), racemes lax with 15 flowers or more rarely 20 flowers (vs. congestous with over 30 flowers), inconspicuously villous and setulose-viscous branches (vs. densely setose-viscous and villous), leaflets glabrous on both surfaces including margin (vs. pubescent on both surfaces with ciliate margin), and styles glabrous (vs. pubescent).

Chamaecrista tenuicaulis differs from C. decumbens by its delicate, setulose-viscous and villous branches (vs. robust and glabrous), subdecumbent branches (vs. creeping), pubescent and setulose stipules (vs. glabrous), leaflets 0.9–1.4 × 0.6–1.2 cm (vs. 1.2–3 × 1.5–3.2 cm), proportion leaflets/rachis ≤ 0.5 cm (vs.≥ 0.7 cm), bracts 1.5–1.8 mm (vs. 2.1–5 mm), axis of the inflorescence and pedicels slender (vs. robust), flowers with pedicels subequal conferring the inflorescence the aspect of typical racemes (vs. floral pedicels conspicuously unequal conferring the inflorescence a corymbiform aspect), fruiting pedicel 1.7–3 cm long (vs. 3.5–6, rarely 8 cm long), adult leaves usually with 4–7 pairs of leaflets (vs. 2–4 pairs of leaflets), and racemes with 6–15 flowers (vs. 17–28 flowers). Furthermore, according to our field observations, C. decumbens grows preferentially on clayey soils and its flowering and fruiting occur in the rainy season, between December and March, while C. tenuicaulis grows on litholic soils and produces flowers and fruits during the dry season, from June to September.

Also, C. tenuicaulis superficially resembles C. altoana ( Irwin & Barneby 1978: 122) Irwin & Barneby (1982: 654) and C. strictula ( Irwin & Barneby 1978: 120) Irwin & Barneby (1982: 654) in its general aspect and foliar traits (number and shape of leaflets). However, the characteristics mentioned in Table 1 serve to differentiate them.

Figures

FIGURE 1.Chamaecristatenuicaulis. A. Flowering branch. B. Detail of the branch showing the indumentum. C. Stipule. D. Leaflet. E. and F. Types of leaflet apex. G. Portion of the inflorescence axis showing the indumentum. H. Bracts. I. Bracteoles. J. Flower bud. K. Flower. L. Sepal. M. Petals. N.Androecium and gynoecium. O. Stamen. P. Gynoecium. Q. Fruit. R. Seed, side view.All from A. O. Souza et al. 554 (UFG). Drawn by Cristiano Gualberto.